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08 JK 23S - Colorado Jeep Club No. 204
Too much to list - see my profile for details on build
NRA Life member
"It takes a special kind of stupid to believe criminals will follow gun laws."
I do not consider myself a smartass. I point out the obvious, search for the truth, and speak fluent sarcasm. I am, by experience, an accomplished curmudgeon.

So with a gear change your axle warranty would be voided? My dealer gave me a vehicle lift form that stated any lift up to 4" would not void the warranty. But I dont want to go too big if I cant have a gear change!

^^^ My understanding is warranty is only void if they can prove the mods did the damage. Seriously, what is going to happen to an axle that involves a "good" gear swap? Bending the axle tubes, snapping an axle shaft, bending the axle "C"s - ie. a Wrangler under hard use - I can't see any of these being covered by warranty anyways (???). And for obvious reasons - if you do have ring and pinion and/or bearing damage down the road - the dealer isn't going to get you a new set of 4.56's or 4.88's when they don't stock them. Now a "sloppy" gear swap - one where you have gear/pinion, bearing cap, or housing damage due to a bad install is another story... a dealer can't be responsible if your gear swap caused the damage. However, with a proper shop install (or personal install if you have the knowhow/tools) I don't think you'll have any problems with a voiding warranty (but that's just my opinion!!!).

As far as lifts voiding warranty - that is dependant on the dealer themselves. My dealer told me any size tire over stock size with a lift over 2" voids warranty. Too late after I already bought it - I love my Jeep, but this will be the last vehicle I buy from them! I might be in "a different boat" than you, but I lifted and slapped 35"s on her anyways. Forget the warranty, if it comes to it I'll just have to kick up a fuss I guess (knock on wood!)...

So what these charts are telling us is that the creator of the chart believes that 99.9% of all JK's, with 3.8L motors, were improperly geared when built (I'll leave room for 0.1% to be "properly" geared due to customer orders)? I'm having trouble believing that.

So what these charts are telling us is that the creator of the chart believes that 99.9% of all JK's, with 3.8L motors, were improperly geared when built (I'll leave room for 0.1% to be "properly" geared due to customer orders)? I'm having trouble believing that.

I have a 2011 Unlimited with automatic. Would I say that it's ideal? No, but I also don't have "minimal use of OD", even with 33" tires (that don't even put it into the yellow band). From my experience with my JK and the ones that I test drove, 4.10 gears with 33" tires should have a JK almost to the bottom end of the "acceptable" range (prob not in it, but 1 notch outside). 4.56 would probably be the best choice, for auto tranny and 33's (4.88 with 35's).

In addition, according to the charts the 3.21 geared manual tranny JK's should have 28" tires (technically 27.5, but most "28's" are that size) to barely make it into the acceptable range. I didn't drive any manual tranny JK's but I find it hard to believe that 28's with 3.21 gearing is "ideal".

I kind of over stated my point, because stock manual Rubi's and Sahara's would be in the acceptable range, but the point remains that these charts are a little biased towards higher gear number.

Most guys on here will tell you to save your cash and use it for gears .....the intake & exhaust thing just doesn't make ponies on this engine . Probably would need a cam and a retune to be able to use the intake & exhaust . Are you auto or 6spd. ?

I'm not looking to run 35's, but I have the infamous auto tranny, so I've been looking into the same question as the OP. After a lot of research, I've come to the conclusion that this is the best plan (i.e., save the cash for intake & exhaust and put it into gears). Even if you loss an MPG or two, because you are running higher RPM (although, it shouldn't), 2 MPG means 10% more gas consumed. At $4 per gallon, that means $2,000 in gas over 100K miles (assuming 18MPG average). $6,000 supercharger or $2,000 in gas.

I'm not looking to run 35's, but I have the infamous auto tranny, so I've been looking into the same question as the OP. After a lot of research, I've come to the conclusion that this is the best plan (i.e., save the cash for intake & exhaust and put it into gears). Even if you loss an MPG or two, because you are running higher RPM (although, it shouldn't), 2 MPG means 10% more gas consumed. At $4 per gallon, that means $2,000 in gas over 100K miles (assuming 18MPG average). $6,000 supercharger or $2,000 in gas.

I have a 2011 Unlimited with automatic. Would I say that it's ideal? No, but I also don't have "minimal use of OD", even with 33" tires (that don't even put it into the yellow band). From my experience with my JK and the ones that I test drove, 4.10 gears with 33" tires should have a JK almost to the bottom end of the "acceptable" range (prob not in it, but 1 notch outside). 4.56 would probably be the best choice, for auto tranny and 33's (4.88 with 35's).

In addition, according to the charts the 3.21 geared manual tranny JK's should have 28" tires (technically 27.5, but most "28's" are that size) to barely make it into the acceptable range. I didn't drive any manual tranny JK's but I find it hard to believe that 28's with 3.21 gearing is "ideal".

I kind of over stated my point, because stock manual Rubi's and Sahara's would be in the acceptable range, but the point remains that these charts are a little biased towards higher gear number.

So here's the long term deal. 08 unlimited 3.73 gears and heavy 35" tires (86lb ea). I've had it since new it is a daily driver and traveller, spends 90% of the time on the highway.
Programmed with a Superchips and I run OD OFF ( equivalent to 5.13 gears) all the time at an average 17mpg.

When originally designed the Wrangler package was sufficient with stock wheels and an auto with 3.73 stock 32" tires and was capable of 23 mpg, however, as soon as you step up even one size in tire the OD, in my opinion, is useless. It constantly kicks on and off which stresses the drivetrain and is harder on fuel. The 3.8's sweet spot is 2100-2300rpm. This is where it get the best fuel economy.

My take is there is absolutely no issue with power with the 3.8 engine itself at lower elevations. The transmission gearing is two ratios too high and that is the issue. Look at the RpM charts and compare rpms vs gears. The final gearing in an 07-11 would have to be 4.56 just to be equivalent to a 12-13 with 3.73. Older automatics did not come factory with 3.21, only the manual trans did with 28" tires.